1. Field
Embodiments of the present invention relate to an electro-hydraulic brake system to control hydraulic brake force according to a change in regenerative brake force.
2. Description of the Related Art
A hybrid electric vehicle includes more than one power source, such as an electric motor (drive motor) and an internal combustion engine, and selectively uses power of the engine or the electric motor according to the load and velocity of the vehicle. The motor also functions to convert the remaining energy into electric energy. Thus, the hybrid electric vehicle may achieve high fuel efficiency and low environmental pollution.
In the above described hybrid electric vehicle, drive wheels of the vehicle are rotated by the electric motor that is operated by electric energy during traveling. In this case, the utilization efficiency of electric energy in the electric motor may be very important. To this end, if a vehicle driver commands deceleration or braking, the electric motor functions as a generator to generate electric energy. The generated electric energy is stored in a capacitor. While the electric motor functions as a generator, brake force is applied to the wheels of the vehicle. This is referred to as regenerative braking. In conclusion, the brake force applied to the wheels is the sum of regenerative brake force generated by the electric motor and hydraulic brake force generated by a hydraulic mechanism.
In other words, driver requested braking may be satisfied by generating only the hydraulic brake force that corresponds to a difference between the regenerative brake force generated by the electric motor and brake force demanded by the driver.